The 33-year-old Williams started well, winning all-but four points on her first serve as she took the opening set, and grabbing her sole break opportunity to get ahead in the match.
But the American veteran's serve was dismal in the second set as she was broken three times, while Zahlavova Strycova lost just three points on her own serve to square things up.
The final set was far more even and swung back and forth, with both players breaking each other as it looked like going to a tie-break - only for Williams to break once more in the 12th game to clinch a-second round spot.
Williams's sister Serena is also taking part in the tournament, and faces Jana Cepelova later on Tuesday.
Seventh seed Sam Stosur also came through a tough match, beating Kazakhstan's Yaroslava Shvedova 6-3 5-7 6-1 in their second round clash.
7-Samantha Stosur (Australia) beat Yaroslava Shvedova (Kazakhstan) 6-3 5-7 6-1
14-Andrea Petkovic (Germany) beat Lesia Tsurenko (Ukraine) 6-7(2) 6-4 6-1
Lourdes Dominguez Lino (Spain) beat Anabel Medina Garrigues (Spain) 6-3 6-2
11-Venus Williams (U.S.) beat Barbora Zahlavova Strycova (Czech Republic) 6-3 0-6 7-5
13-Elena Vesnina (Russia) beat Anna Karolina Schmiedlova (Slovakia) 6-2 6-1
Vania King (U.S.) beat Julia Glushko (Israel) 4-6 7-5 6-3
16-Zhang Shuai (China) beat Hsieh Su-Wei (Taiwan) 3-6 7-6(5) 7-6(0)
12-Daniela Hantuchova (Slovakia) beat Shelby Rogers (U.S.) 7-5 7-5
WTA Monterrey first round:
8-Monica Puig (Puerto Rico) beat Olga Puchkova (Russia) 6-0 6-3
6-Magdalena Rybarikova (Slovakia) beat Olga Govortsova (Belarus) 6-3 3-6 6-2
Luksika Kumkhum (Thailand) beat Dalila Jakupovic (Slovenia) 7-5 6-0
- Sports & Recreation
- Barbora Zahlavova Strycova